Abstract: Zhongguan iron mine is a water-contained mine attributed to Ordovician Karst water in limestone and it is threatened by water-inrush during the mine construction. In this paper, a water-inrush case at -260 m level has been studied to find out the mechanism based on the combined research of regional tectonic conditions and dynamic monitoring results of the underground water level. The results have shown that the water-inrush is caused by the activation of X1 buried fault and the formation of water-inrush channel. The channel contributes to building the hydraulic connection between the driving face and the aquifer after the fault evolved from water-resisting to water-conducting due to several times of roof coving led by X1 fault exposed in the tension-deformation zone under artificial mining. On the basis of the water-inrush mechanism, the countermeasures summarized as “driving with detection and driving after detection; water plugging taking the first place or with drainage together” for preventing the karst water-inrush at the roof of driving face in -260 m level are established during the mine construction. Thus, construction of tunnels at -260 m level under karst conditions with safety and high proficiency has been achieved.

Key words: Zhongguan iron mine, water inrush, fault reactivation, Ordovician Karst water, countermeasure